The rewrite argument allows you to define the permalink structure of your posts when viewing the single post. For example, you may want to have a structure like yoursite.com/cool/post-name. WordPress will set up a default structure based on your taxonomy name. The rewrite argument can be set to true, false, or an array of values. It takes two arguments:

if i turn the 'rewrite' value to false on the custom post type it doesn't make any difference until I remove the videos taxonomy.

Is this something which I shouldn't be doing? I do have a pretty complicated reason for naming both custom post types and taxonomy the same (mainly due to auto creation of a taxonomy term when a custom post is added)

Hey tbp278, I just found this support thread because of the exact same problem.

It does appear that its an issue having Custom Post Types and Custom Taxonomies that have the same name. I had 'Portfolio' for both and the posts where 404'ing, I've just changed the taxonomy to 'Work' and the posts are now working fine.